An unparalleled range of photonic nanocomposites has been developed utilizing surface engineering over preformed nanoparticles. These nanocomposites cover a number of organic polymers as host materials. By controlling a loading level of inorganic nanoparticles (e.g., nano-TiO₂) within a polymer host, important optical parameters including the refractive index (n) can be varied over 50~100 % with respect to the corresponding polymer matrix. This refractive index control capability enables a large refractive index contrast (Dn) that is a very significant requirement for fabrication of microphotonic devices such as photonic crystals. High levels of nanoparticle dispersion within a polymer host can be achieved even at loading levels up to 60 wt% to assure low scattering, i.e., transparent coated films in the infrared and visible light regions for photonic crystal applications. This paper presents nano-engineered polymer-based photonic crystal materials and processes to make them. Use of very uniform nanoparticles preformed by laser-driven chemical reaction is vital for successful fabrication of optical-class composite films and described here. Major benefits out of the current approach are discussed including (a) high Δn, (b) easy-to-fabricate 'hetero-interface', a minimal unit of periodic photonic crystal structures, and (c) significant economical benefit.

We report the reduced linear-optics waveguiding efficiency for the signals around 1 560nm as the injection current of a GaAs/A1GaAs multiple quantum well laser diode (lasing wavelength at 840 nm) with a ridge-loading waveguide configuration increased. The decreased waveguide transmission and the more expanded mode profile indicated the variation ofthe effective refractive index distribution in the lateral dimension with injection current. The variation was partially due to carrier diffusion into the regions outside the ridge. Also, enhancements of two-photon and three-photon absorption coefficients with injected carrier density at 1560 nm in the same laser diode device were observed. The results were obtained by calibrating 130 fsec laser transmission data through the laser diode. Such enhancements were mainly attributed to the existence of hole states in the first heavy-hole subband during carrier injection. With the hole states, two-photon absorption in the TE polarization finds the other transition path for a higher transition rate. Such hole states are not so effective to the two-photon transition in the TM polarization.

A laser beam propagating through the atmosphere, undergoes attenuation through absorption and scattering on droplets of fog, clouds, different kinds of precipitation (rain, snow), smoke, dust; as well as it is subjected to a turbulence-induced scintillation. The resulting influence is a decrease of the information capacity of the system, rise of the bit-error rate and deterioration of the pointing accuracy at the receiver. Whereas the attenuation caused by scattering can be predicted by monitoring the weather conditions, the effects induced by turbulence have a random character and need to be overcome via some dynamic compensation procedure. This can be done using the phenomenon of wavefront reversal by means of dynamic holograms, which allows automatic compensation of disturbances. The unique advantages given by holographic technique make it rather promising to develop a relatively simple and reliable module for correction of atmospheric distortions in laser communication systems. One of the main problems though is to find an optimal medium for hologram recording that allows fast write-read-erase operation, high diffraction efficiency, high stability of characteristics and long lifetime.

Photonic crystal waveguides in InP-based heterostructures are studied experimentally and theoretically. The waveguides are fabricated in an InP/GaInAsP/InP low index contrast heterostructure using Ar/Cl₂ Chemical Assisted Ion Beam Etching, and characterized using the end-fire method. The obtained experimental near-infrared transmission spectra are further analyzed by comparing with theoretical results calculated by the finite-difference time-domain method. A loss of 1 dB/100 μm in the photonic crystal waveguides is demonstrated. The mini-stop bands, positioned in agreement with our theory, are observed. In-plane cavities with photonic crystal boundaries inside the waveguide are also realized. A quality factor of 400 for a 6 mm long cavity is obtained.

Transient and static thermal response of high power single-mode laser module has been simulated using finite element method (FEM). FEM modeling revealed the time constants of heat propagation in lateral direction and in vertical direction. The time constants calculated by FEM modeling in the microsecond scale and the sub-millisecond to millisecond scale were experimentally verified by a time-resolved far-field optical measurement and a transient forward-voltage measurement respectively. It is shown that the active region, semiconductor substrate and the solder-submount each contributes about 35%, 50% and 15% to the total static thermal resistance of the laser package.

This paper reviews recent progress of high-power 14xx-nm pump lasers using AlGaInAs/InP material. This material has superior temperature characteristics to conventional InGaAsP/InP. As a result, it is more suitable for high current and high efficiency operations as well as uncooled applications for the high power 14xx-nm lasers, which are required for advanced optical amplifications. The laser module consists of a laser chip coupled to a fiber lens and mounted on a thermoelectric cooler in a standard butterfly package. The wavelength of the laser can be stabilized with an external fiber Bragg grating (FBG). We have demonstrated a maximum module fiber output power of 550mW at 1.75A and characteristic temperatures of T₀ = 99K and T₁ = 348K over a range of chip heat-sink temperatures from 15°C to 50°C. To the best of our knowledge, these are the highest efficiency and temperature characteristics from a single-mode 14xx-nm semiconductor laser module capable of over 0.5W fiber output power. At a chip heat-sink temperature of 70°C, a power of 360mW was obtained for a laser module with FBG, which is the highest reported to date for any wavelengths from 1300nm to 1600nm and would enable uncooled applications of the 14xx-nm lasers in the future.

This paper reviews the recent progress in 14XXnm-band pump lasers of new design concepts. One is the new packaging scheme with integrating multiple laser stripes and a polarization beam combiner, which brings various benefits in cost-performances of the optical amplifier both in EDF (Erbium doped fiber) and Raman configuration. This "hybrid" designed pump lasers offer stable low-DOP (degree of polarization) of 5% with the standing-alone laser package, and demonstrated the potential optical output beyond one watt with the significant saving factor in board-spaces and electrical power consumption. The other is the inner-grating multi-mode (iGM) chip design, which integrates the wavelength stabilizer into the laser stripe and maintains stable multi longitudinal-mode oscillation. The "iGM" laser shows very low RIN (relative intensity noise) less than -150dB/Hz together with suppression of SBS (stimulated Brillouin scattering) in the transmission fiber. We conclude that these new pump lasers, hybrid and iGM lasers, are promising candidates to the 14XXnm-band pump sources for co-propagating Raman-amplifier as well as EDF-amplifiers of next generation.

The band structures of dispersive photonic crystals are numerically investigated. Based on the fmite-difference time-domain (FDTD) method with some auxiliary variables, time-stepping formulas are derived to compute the evolution of electromagnetic fields. The photomc crystals made of dispersive materials can be described either by the Lorentzian model or by the Drude model. In this paper, we describe how to use the time domain technique to calculate the dispersion relation of photonic crystals and then introduce the recursive convolution scheme to treat the photonic crystals with frequency-dependent materials. Band structures of photomc crystals without dispersion are calculated with the conventional FDTD time-stepping formulas and those with Lorentzian type dispersion and Drude type dispersion are also calculated with the recursive convolution scheme.

Recent progresses of semiconductor photonic crystals including both three-dimensional (3D) and two-dimensional (2D) crystals are reviewed. On the 3D photonic crystals, we first review our approaches to fabricate full 3D photonic bandgap crystals at near-infrared wavelength region. Recent experimental results on an introduction of light emitters and defects into the 3D photonic crystals are then presented. On the 2D photonic crystals, we report two types of devices. One of this is a 2D photonic crystal laser, where the multi-directional distributed feedback effects and the control of polarization are described. The other is a channel add/drop filtering device. The theoretical and recent experimental results focusing on the polarization characteristics of the devices are explained.

Active photonic lattices (APLs) of large index step have been used, as early as 1988, for effective lateral-mode control in large-aperture (100 microns) high-power coherent devices. Photonic-bandpass (PBP) structures relying on long-range resonant leaky-wave coupling, so called ROW arrays, have allowed stable, near-diffraction-limited beam operation to powers as high as 1.6W CW and 10W peak pulsed. Photonic-bandgap (PBG) structures with a built-in lattice defect, so called ARROW lasers, have provided up to 0.5W peak-pulsed stable, single-mode power and hold the potential for 1W CW reliable single-mode operation from apertures ~10 microns wide. The solution for high-efficiency surface emission, from 2nd-order DFB/DBR lasers, in an orthonormal, single-lobe beam pattern was found in 2000. Recently, single-lobe and single-mode operation in a diffraction-limited beam orthonormal to the chip surface was demonstrated from 1.5mm-long DFB/DBR ridge-guide lasers. That opens the way for the realization of 2-D surface-emitting, 2nd-order APLs for the stable generation of watts of CW single-lobe, single-mode power from large 2-D apertures, as well as scalability of such devices at the wafer level.

The principle of operation and the design techniques for various types of the optical demultiplexers are reviewed. The results for two-channel optical demultiplexer based on optical directional coupler configuration are presented. The device for separating two wavelengths with 4 nm spacing is designed on the Silicon substrate in SiO₂/SiO₂-TiO₂/SiO₂ rib waveguide. The rib waveguide design techniques using the effective index method are described. The propagation of the two wavelengths through the device is calculated using the computer tools based on the beam propagation method (bpm). The dependence of the device length required for separation of the two wavelengths on the rib waveguide parameters is studied. The waveguide rib width and separation between the parallel waveguides are the parameters those affect the value of the length required for separating the two wavelengths to a greater extent. The guide thickness inside the rib also has considerable effect on the device length. The clad thickness and rib height, however, were found to be the least affecting parameters. The optimization techniques for the rib waveguide and the coupler parameters for achieving the demultiplexing with the minimum length of the device are explained. The proposed fabrication techniques for the SiO₂/SiO₂-TiO₂/SiO₂ rib waveguide are presented.

In this paper we present simple interferometric technique for thin film testing with GaAs:Cr adaptive photodetectors based on the effect of the non-steady-state photoelectromotive force. The technique needs no special vibroinsulation and automatically adjusts and keeps the operation point of the interferometer. Two different interferometric schemes with GaAs:Cr adaptive photodetectors are reported. A modified Mach-Zehnder interferometer with adaptive photodetector is used for the measurement of piezoelectric coefficient of the thin film. A two-beam polarization interferometer with adaptive photodetector is used for the measurement of effective differential Pockels coefficient r_e = r₃₃-(n₀/ne)³r₁₃. It is shown that two-beam polarization technique allows measurement of the Pockels coefficient of thin film with a strong Fabry-Perot effect that usually presents in ferroelectric thin film. Strong hysteresis effect with a slightly asymmetric form of the hysteresis loop was observed at the dependence of d₃₃ and r_e coefficients of the PZT thin film versus DC electric field. The values of d₃₃ and r_e are in agreement with known data.

We fabricated all-optical polymer devices such as Mach-Zehnder modulator and 1x2 switch using a polymer doped with photoresponsive dyes. The refractive index change of the photoresponsive dyes by irradiation of light was utilized to fabricate switching and modulation devices. All-optical Mach-Zehnder modulator and switch are demonstrated which are composed of a polymer waveguide doped with the dyes in the core and a thick light blocking metal layer on the waveguide. The metal layer was opened on one arm of the Mach-Zehnder modulator and 1x2 Y-branch switch, so that only one arm could be irradiated by control light, thus allowing a changing of refractive index. The optical modulator and switch exhibited an extinction ratio of about -12 dB and a crosstalk of -14 dB at a wavelength of 1.55 μm respectively. A simple kinetic model developed to delineate the refractive index change in the dye doped polymer film was applied to predict the evolution of the modulation characteristics. We have also fabricated polymeric wavelength filters with Bragg grating. The surface relief grating was formed using an azobenzene polymer film and used as an etch mask to transfer the pattern to polymer waveguides by reactive ion etching (RIE). The grating period was 5OO nm and the depth was 3O nm with 10-mm-long grating length. A crosstalk of -20 dB at the Bragg wavelength and the 3-dB transmission bandwidth of 0.2 nm were obtained from the device.

A polythiophene-doped polymethylacrylate which have absorbance in visible region was synthesized by plasma polymerization, and its fluorescence spectra was studied. The absorption peak was 440nm, the fluorescence emission of spectra was 570nm. The intensity of the fluorescence emission of the polymer was higher than that of the polymer synthesized by radical polymerization. It is reasonable to suppose that chemical reaction of plasma polymerization was mild compared with radical polymerization.

High concentration rare-earth metal ion chelates, Europium 6,6.7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5,- octanedionate, (Eu-FOD) doped PMMA fiber and film were successfully prepared for the first time by casting solution method and gel spinning method. The optical and photoelectric characteristics of Eu(3+)-FOD doped PMMA film and fiber were investigated. Amplified spontaneous emission (ASE) from the Eu-FOD doped PMMA film and fiber was observed. The high concentration Eu-FOD-doped PMMA fiber and film sample exhibited lasing threshold as low as o. 15 mJ/ cm² when pumped with a 355 nm pulsed laser beam.

In this paper, the basic principle, details of fabricating process and measuring results were described for a polymer/Si arrayed waveguide grating (AWG) multiplexer around the central wavelength of 1.550 micron with the wavelength spacing of 1.6nm. The fluorinated polymer was used to fabricate AWG to reduce the optical loss, but the fluorinated material was expensive, so we initially adopted the polymer of polymethylmethacrylate(PMMA) type to go on technologic research. The regulated curve of refractive index was given for the core polymer. In order to obtain better shape of the waveguide after the reactive ion etching (RIE) using oxygen, an aluminum film as mask was used on polymer instead of conventional photoresist as mask. In order to reduce radiation loss of underciadding layer to Si substrate, the underciadding layer thickness was increased to 11 micron through two times of spin-coating, thus the radiation loss was reduced to the order of 0.001dB. The measuring results indicates fabricated optical waveguide achieved single-mode transmission.

In this paper, a 9 X 9 Polymer/Si AWG was designed and fabricated. The cladding material is poly-methyl-methacrylate-co-glyciclyl methacrylate (PMMA-GMA) and the core material is the mixture of PMMA-GMA and bis-phonel-A epoxy. During the fabrication process of the Polymer/Si AWG device, We used aluminum as mask on polymer instead of conventional photoresist as mask. The results show that the device is good for the wavelength division multiplexing (WDM) system. The output characteristics of the device were measured by a system based on the tapered fiber. The results show that our polymer/Si AWG meets the designed device well.

A rare-earth chelate, Europium 6,6.7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5,-octanedionate, (Eu³⁺-FOD) doped DNACTMA complex as fiber and film materials was prepared by casting solution method and gel-spinning method. The Eu-FOD-DNA-CTMA complex was luminescent and has 750 μs of fluorescence lifetime, sharply-spiked emission spectra, excellent film and fiber formability, moderate absorption (40000M^-1cm^-1) at 327 nm and high quantum yield forlanthanide emission. By comparison of fluorescence lifetime of Eu-FOD doped DNA-CTMA solid matrix with that of Eu-FOD doped in PMMA, it was clear that energy transfer from DNA to FOD leads to enhancement of fluorescence emission at 613 nm. Analysis results for fluorescence spectra and fluorescence relaxation time of Eu³⁺ doped in the materials indicated that Eu³⁺-FOD is chemically bond within the DNA-CTMA matrix. Amplified spontaneous emission (ASE) at 612 nm by pumping with UV laser (355 nm) was observed in the materials. Fluorescence lifetime of the Eu-FOD doped in the DNA-CTMA solid matrix was evaluated to be 750 μs, which is ca. 230μs longer than that of Eu-FOD doped in PMMA solid matrix. Efficient Energy transfer from base of DNA to FOD, then to Eu, occurred when irradiated by UV light or 355 laser beams.

A ridge-waveguide, InGaAs/GaAlAs/GaAs, 980 nm, pump laser-diode emitting more than 600 mW of kink-free power and a FWHM divergence angle less than 22 degrees using an asymmetric-waveguide structure is presented. No catastrophic optical-damage was observed on p-up mounted devices up to a quasi-CW output power of 2 Watts where the power was limited by thermal effects.

A theoretical model is presented to calculate the fiber coupling efficiency and alignment tolerances for the case of a 980nm pump laser diode directly coupled to a round-shaped cylindrical lensed fiber (CLF). Both radius and wedge angle of the round-shaped cylindrical lens are optimized for maximal coupling efficiency. It is found that with proper design, a coupling efficiency up to 98% may be obtained theoretically. The alignment tolerances for all three directions (vertical, horizontal and axial offsets) are also calculated, and found that the vertical offset tolerance is critical and presents the biggest challenge in packaging. In addition, it is also found that both LD-to-CLF distance and lens shape affect the vertical offset tolerance, and can be varied to improve this tolerance.

Inductively coupled plasma (ICP) dry etching technique has been adopted to form narrow high-mesa ridge waveguide structure in a high-speed integrated EA modulator. A 3dBe bandwidth of over 12 GHz has been achieved without the use of polyimide in the DFB laser integrated EA modulator. Meanwhile, integrated device with a threshold current as low as 12 mA has been demonstrated by optimization ofthe wavelength detuning.

A novel structure ofGaAs/GaAIAs multi-quantum well (MQW) traveling wave (TW) Mach-Zehnder modulator (MZM) with coplanar strips is proposed. This device uses n⁺ heavy doped layer to obtain velocity match. Then the Method of Lines is applied to characterize the influence ofmetallization thickness and conductivity loss on the velocity match and impedance match. With optimum parameters ofthe structure, the bandwidth over 80GHz is obtained.

This paper presents an overview of our study on approaching and achieving micron-scale or nano-scale integrated photonic devices and circuits. We examine the scientific and technological issues and challenges concerning the miniaturization and integration of photonic devices and circuits in micron or submicron scale. We will discuss the size effects, quantum effects, high-field effects, proximity effects, optical interference effect, nonlinear effects, and thermal effects in the process of miniaturization and integration of photonic devices and arrays. Models of our study include the devices and arrays of vertical cavity surface emitting microlasers, microdisk lasers, arrayed waveguides, micro-ring resonator devices and arrays and directional couplers, multi-mode interference devices, and spot-size converters. Issues and challenges for two-dimensional integration and three-dimensional integration are discussed based on realisitic examples. We will also discuss similar effects in micro/nano-scale electronics, so that they can provide the lessons from which the micro/nano-photonics can benefit in a complementary manner.

By measuring the spontaneous emission from normally operating ~1.3um GaInNAs/GaAs-based lasers grown by MBE and by MOVPE we have quantitatively determined the variation of monomolecular (defect-related ~An), radiative (~Bn2) and Auger recombination (~Cn3) as a function of temperature from 130K to 370K. We find that A, B and C are remarkably independent of the growth method. Theoretical calculations of the threshold carrier density as a function of temperature were also performed using a 10 band k·p Hamiltonian from which we could determine the temperature variation of A, B and C. At 300K, A=11x10-8 sec-1, B=8x10-11 cm3 sec-1 and C= 6x10-29 cm6 sec-1. These are compared with theoretical calculations of the coefficients and good agreement is obtained. Our results suggest that by eliminating defect-related currents and reducing optical losses, the threshold current density of these GaInNAs/GaAs-based edge-emitting devices would be more than halved at room temperature. The results from studies of temperature and pressure variation of ~1.3um VCSELs produced by similar MBE growth could also be explained using the same recombination coefficients. They showed a broad gain spectrum and were able to operate over a wide temperature range.

In this paper, we will present the recent progress of electrically-pumped directly-modulated tunable 1550 nm VCSEL development at Bandwidth9. The device is fabricated from an all epitaxial VCSEL structure grown on an InP substrate, with a monolithically integrated tuning arm for continuous wavelength tuning. We have demonstrated over 1 mW CW output power and over 20 nm tuning range in C-band and error free transmission performance at 2.5 Gbps over 100 km SMF-28 fiber. The reliability test data of the tunable VCSELs shows a projected failure rate of less than 400 FITS.

We have developed temperature insensitive high-efficiency LDs that can operate at wavelengths around 1.3 um for TOSA (Transmitter Optical Sub-Assembly) modules, which are our proposed light source solution for compact transmitters. Since the modules should be used without temperature controllers, a high slope efficiency and high output power operation at over 85degC is essential for LDs. We eliminated the leakage current flowing outside of the active layer using a buried-hetero structure. This resulted in excellent lasing characteristics. The slope efficiency at 25degC and 85degC was 0.49 W/A and 0.38 W/A, respectively. The slope efficiency degradation defined as a ratio of the slope efficiency value at 85degC to that at 25degC was -1.1dB, which to our knowledge is a record value to be reported for practical InGaAsP DH LDs. Excellent uniformity and reproducibility for lasing characteristics of 85degC were verified through multiple wafer runs. The fairly stable long-term operation test of ASM LDs was performed and estimated MTF (Median Time to Failure) at 85degC-10mW conditions was over 1 x 105 hours. Using newly developed ASM LDs, we have assembled the world smallest TOSA modules that could be realized for suitable light source solution under severe ambient temperature conditions.

The influence of high-temperature (>870°C) rapid-thermal-annealing (RTA) induced cracks on the laser performance fabricated with GaAs-AlGaAs quantum-well microstructures is reported. The effects were examined and characterized after quantum-well intermixing within an epitaxial structure capped by either SiO₂ or SrF₂ layers. The results show clearly that the density of surface cracks strongly depend on the atomic interdiffusion between the well and the barrier layers, and on the quality of the dielectric caps as well. In addition to the detailed analysis of the cracking effects on the laser performance, an effective way of reducing the density of RTA-induced cracks was also explored for the dielectrics grown by plasma-enhanced chemical vapor deposition under a low-stressed condition.

Modern trends in design of semiconductor lasers are reviewed. In one novel design, light propagates at some angle with respect to multilayer interference mirrors (MIRs), and the MIRs and the cavity are optimized for the tilted photon propagation. "Tilted cavity" laser (TCL) gives wavelength-stabilized operation in edge and (or) in surface direction and does not require materials having large difference in refractive indices. In a different concept, a high-order mode filtering in structures with periodically modulated refractive index containing a "defect" allows realization of a stable narrow beam divergence fundamental mode lasing in both edge-emitters and vertical-cavity surface-emitting lasers (VCSELs). Using of electrooptical modulators based on quantum confined Stark effect in VCSELs and TCLs allows a significant wavelength tuning range, ultrahigh-speed operation and direct wavelength adjustment to resonant cavity photodiode (RCPD) or tunable RCPD. Different types of tunable semiconductor optical amplifiers, switches, filers may become possible. New generations of cost-effective intelligent telecom systems with direct, ultrafast and wavelength adjustable connection between consumer devices and the storage or processing cites may be realized.

AlGaInAs/InP strained MQW reversed-mesa RWG structure is proposed to reduce leakage current and improve linearity, and applied to make high linearity and high power 1.3μm DFB-LD. For 1.3μm AlGaInAs strained MQW DFB LD, the lasers operated with 10mA threshold current, 0.48mW/mA slope efficiency for one facet, 45dB SMSR. The -3dB cutoff frequency is 14GHz, and the eye pattern is opened widely at 10Gb/s. Under PAL 59 channels test, output power exceeds 15mW with COS<-69.4dBc, CTB<-69.4dBc, CNR<-52dB, which is the first reported RWG 1.3μm DFB-LD for optical CATV application. This implies that AlGaInAs/InP strained MQW reversed-mesa RWG structure could effectively reduce leakage current.

Low threshold semiconductor lasers with etched facets have been fabricated by inductively coupled plasma (ICP) dry etching technology. To ensure vertical and smooth etched-facets, a novel C1₂/CH₄/Ar mixture has been adopted for the ICP etching process. The typical threshold current of etched-facet lasers is about 1 8 mA, which is as low as that of lasers with cleaved-facets and similar cavity length.

This paper presents a time-domain traveling-wave algorithm for the modeling of the large signal dynamic response of a distributed feedback laser integrated with a Mach-Zehnder modulator. The influence of residual optical feedback from the output of the modulator facet on the dynamic frequency chirp is studied. It is found that the difference in frequency chirp between the turn-on and -off states (i.e., adiabatic chirp) of a π/2 shifted 2x2 Mach-Zehnder modulator is minimal and is independent of the residual optical feedback. In addition, it can be shown that the presence of chirped frequency spikes (i.e., transient chirp), due to the change in refractive index as a result of the rapid variation of the bias voltage, can broaden the linewidth and distort the spectrum of the modulated optical signal.

The well number and the cavity length of 1.55mm wavelength In_1-x-yGa_yAl_x MQW DFB lasers are optimized using a simple model. A low threshold, high maximum operating temperature of 550-560K ,and high relaxation oscillation frequency of over 30 GHz MQW DFB laser is presented.

This paper provides prospects and current status of quantum-dot semiconductor optical amplifiers (SOAs) and their comparison with bulk and quantum-well technology, based on our pioneering work covering the proposal of their promising features, subsequent experimental demonstrations, and the design of all-optical quantum-dot switching modules. The proposed promising features are diverse; high-saturation power, high-speed amplification up to 160 Gb/s under gain saturation without pattern effect, high-speed cross-gain modulation up to 160 Gb/s without pattern effect, multiple-wavelength processing over broad gain spectra, and symmetric wavelength conversion by four-wave mixing. The operation theory of quantum-dot SOAs is provided in order to treat various aspects unique to quantum dots such as spatial localization, retarded carrier relaxation, and inhomogeneous and homogeneous broadening. Pattern-effect-free amplification at 10-40Gb/s, wavelength conversion by the cross-gain modulation at 10-40Gb/s, and symmetric wavelength conversion by four-wave mixing are experimentally demonstrated in 1.3-micron InGaAs/GaAs quantum-dot SOAs. All-optical quantum-dot switching modules are proposed, which we expect to work in the next-generation flexible all-optical photonic networks.

In order to improve the coupling efficiency of semiconductor optical amplifiers to single-mode fibers, a model of tapered-rib semiconductor optical amplifier is presented in this papers. The effects of the refractive index of the waveguide region and the structure of tapered-rib waveguide on the expanded output-mode of tapered-rib waveguide are studied and calculated by using the finite element method. A coupling efficiency of 95% is obtained by optimizing the parameters and the structure of the tapered-rib semiconductor optical amplifier.

Amplification is a key function in optical networks. Traditionally, amplifiers have been used to compensate losses in optical fiber, enabling longer communication links. Today, amplifiers are being used in increasingly diverse functions ranging from power boosting of transmitters to loss compensation in optical add-drop nodes. Common to all these applications is the requirement to meet optical performance parameters within demanding cost, size and power constraints. The single-chip linear optical amplifier (LOA) is a solution that offers advantages as a discrete module, but also enables higher levels of integration. Examples of system performance and integrated solutions, utilizing the LOA, will be shown.

We had fabricated a 1.5μm tilted superluminescent diode (SLD) integrated with a semiconductor optical amplifier (SOA). High superluminescent power 70mW was obtained at lower pumping level by co-operation of the two sections under pulse condition. The spectral FWHM is 23nm.

We built a test system to pick up the pattern of light beam from the VCSELs and the EL spectrum simultaneously in order to study the mode behavior when the current applied on the device increased. As a result, we observed that the light spots from the VCSEL seemd to be high-order-mode while its EL spectrum included more than one peak wavelength. Comparing it with the high-order-mode case that we met and defined in VCSELs before, we considered that the mode we observed this time was different from the true high-order-mode in essence. We named it as pseudo-high-order-mode and gave the explanation.

In this paper, we report a high performance, highly uniform, and highly reliable VCSEL platform at LuxNet Corporation. The proprietary design of this VCSEL gives it oxide VCSEL-like performance and an implant VCSEL-like reliability. Threshold currents are between 1 .0 to 2.5 mA, and the slope efficiencies are between 0.3 to 0.5W/A. The threshold current change with temperature is minimal and the slope efficiency change less than ~30% when the substrate temperature is raised from 25°C to 90°C. The eye diagram of LuxNet TOSA operating at 2.5 GB/s with 6mA bias and 10dB extinction ratio shows very clean eye with jitter less than 3Ops. We have accumulated life test data up to 5000 hours at 100°C/2OmA with exceptional reliability. And the WHTOL (85/85) bias at 8mA has passed over 3000 hours. In addition, the overall yield across a 3 inch wafer is over 90%. The chips are now being shipped in commercial quantities. Finally, we will present our preliminary results of 10 Gb/s VCSEL.

We report on recent progress in the design of short-wavelength vertical-cavity surface-emitting lasers (VCSELs) for 10 Gbit/s datacom applications. Topics of interest include differential mode delay characterizations of high-performance multimode fibers and their interplay with transverse single- and multimode VCSELs, flip-chip integrated two-dimensional arrays at 850 nm wavelength, as well as experiments toward the realization of optical backplanes. In the latter case, reliable 10 Gbit/s data transmission has been achieved over low-loss integrated polymer waveguides with up to 1 meter length. Moreover we present VCSELs with output powers in the 10 mW range that are employed in multi-beam transmitters for free-space optical data transmission with Gbit/s speed over distances of up to about 2 km.

We report here on wafer-bonded InGaAs/Si avalanche photodiodes (APDs) demonstrating very low excess noise factors that were fabricated using a high-yield, wafer-scale bonding process. The bonding interface quality was evaluated using high-resolution x-ray diffraction and dark current measurements. Measured dark currents on 20 μm diameter mesas are 25 nA and 170 nA at gains of 10 and 50, respectively. Low excess noise factors, which are predicted due to the superior noise properties of Si as a multiplication layer, were measured to be more than 3 times lower than commercial InGaAs/InP APDs at a gain of 10, and more than 9 times lower at a gain of 50. The corresponding electron/hole ionization coefficient ratio k in these devices is as low as 0.02.

Optical response of both the gate current and the drain current in p-channel InGaP/GaAs/InGaAs double heterojunction pseudomorphic MODFET is reported and analytic models are presented. Based on quantum nature of the two-dimensional carrier statistics in the channel and a new model for the gate current, the overall current variation under optical illumination is explained. The results show power law relation between the current variation and the optical intensity. Near-threshold region in saturation region is found to be most sensitive to the optical intensity variation

In this paper, the growth and device fabrication of AIGaN/GaN HEMTs are investigated by using Metal-Organic Vapor Phase Epi taxy (MOVPE) system. The grown wafer consists of a 3-μm-thick unintentionally doped GaN buffer layer, an undoped AIGaN spacer layer, and a n-doped Al_0.28Ga_0.72N cap layer. The growth condition and the wafer structure are optimized for high performance devices. The devices exhibit a maximum saturation current density of 1000 mA/mm, good pinch off at -5V gate bias and a peak extrinsic transconductance of 180 mS/mm. Further efforts to improve the device performance are also discussed.

Harmonic and rational-harmonic mode-locking of erbium-doped fiber lasers (EDFLs) with wavelength tunability is achieved by seeding optical pulses from a gain-switched Fabry-Perot laser diode that is feedback-injection controlled with the slave EDFLs via optical circulator.

Energy transfer dynamics in fluorozirconate glass doubly-doped with Yb³⁺:Er³⁺ and Ce³⁺:Er³⁺ have been analyzed by using rate equation formalism. For the Yb³⁺:Er³⁺-ZBLAN glass, the macroscopic energy transfer parameters, cross-relaxation coefficients, were derived to be 1.1*10^-17s^-1cm³ and 2.0*10^-17s^-1cm³ for the forward energy transfer (Yb³⁺ → Er³⁺) and the backward transfer (Er³⁺ → Yb³⁺), respectively. After experimentally investigating fluorescence characteristics of Er³⁺ ions in the Ce³⁺:Er³⁺-ZBLAN glass, taking into account of up-conversion and energy transfer effect, a resonant cascade energy transfer model was developed, with which the operating mechanism of the Ce³⁺:Er³⁺-ZBLAN fiber laser was explained theoretically. The potentiality of the rare-earth-codoped fluoride glass as one of the most promising laser materials is demonstrated.

The Rayleigh scattering intensity in fluorine-doped silica glass was found to decrease very effectively with lowering frozen-in temperature of the glass, so-called the fictive temperature, while such reduction becomes less in samples with higher fluorine concentrations. The present result implies that the Rayleigh scattering in fluorine-doped silica glass is affected by concentration fluctuation besides density fluctuation. From the result, we established a simulated annealing effect of the glass on reduction of the Rayleigh scattering intensity.

Hybrid FRA is consists of distributed FRA and discrete FRA. Optimum design of S-band hybrid dispersion compensation fiber Raman amplifier has been researched by OPTIAMP DESIGN 3.3 software (made in Canada Optiwave Corporation) and gain spectrum and gain vs. power of S-band hybrid dispersion compensation fiber Raman amplifier has been researched. The backscattering spectrum of optical fiber has been measured by use 1427nm Raman laser and Q8384 optical spectrum analyzer and Stokes and anti-Stokes ZX band backscattering spectrum has been first observed and discussed, ZX band frequency shift is 1THz, band width 3THz(3dB). Pump on/off small signal gain is 23dB (pump power 700mw; G652 fiber 25.2km and DCF fiber 5.1km) and gain band width is 96nm (1440nm-1536nm). In the experiment, gain spectrum band width is wider than simulated results, practical including Stokes ZX band backscattering gain effect.

A masterly two-stage structure for Erbium-doped superfluorescent fiber source (EDSFS) with high output power and broadband amplified spontaneous emission (ASE) spectrally flattened in both C-band and L-band is presented in this paper. Thereinto, the L-band ASE is generated in the first forward-pumping double-pass stage, and amplified in the second backward-pumping single-pass stage, where a high-power C-band ASE is simultaneously generated. The output ASE with a power of 16dBm and 3dB bandwidth over 61nm is obtained by simulations with the simple structure without any filter, by suitably choosing the structure parameters of the two-stage EDSFS, such as the lengths of Erbium-doped fibers (EDF) in the two stages and the beam splitting ratio of pump powers of the two stages.

This paper reports on optical and optoelectronic properties of DNA-surfactant complex films which were intercalated with a NLO dye, Disperse Red 13(DR-13). Circular dichroism (CD) analysis indicated that the orientation of the azo dye, DR-13 doped in DNA-surfactant complex film was achieved by inserting the dye molecules into the nano-size space between base pairs of DNA. The Disperse Red 13-doped DNA thin film displayed higher THG than that of CS₂ about two orders. On the other hand, SHG signal could not be observed even in the presence of anisotropic ordering of the molecular chromospheres on template of the double helix of DNA, perhaps because of absorption of the dye for SHG light.

Plane wave propagation in chiral plasma and chiral ferrite media is studied in kDB coordinate system. General wave equations and characteristic equations of plane waves propagating along an arbitrary direction in chiral plasma and in chiral ferrites are derived in simple formulations respectively. Four wavenumbers and their corresponding dispersion characteristics in chiral ferrites are resulted for propagation both along and normal to the biasing magnetic field. When plane wave with negative helicity propagates along the biasing magnetic field in chiral ferrites, backward waves emerge.

A Variable Optical Attenuator (VOA) in a simple structure is introduced using the basic principles of internal reflection. The proposed configuration includes a special trapezoid prism-film system which allows a light beam incident twice upon the bottom face and once upon the top face ofthe prism. As a result, a VOA having greater than 20dB dynamic range and less than 0.5 dB Polarization Dependent Loss (PDL) has been demonstrated experimentally.

An improved ATR modulator consisted of a prism-metal-EQ-polymer-metal structure is presented. Unlike the ATR modulator conventional, we change the working interior angle from the surface plasmon resonance to a guided wave resonance. Since the propagation constant is much more sensitive to the electrically induced refractive index change in the poling polymer layer for a guided mode than a surface plasmon mode, so the drive voltage can be accordingly decreased. In our recent experiment, an ATR modulator with 1 GHz bandwidth and a modulation index of 10% at a driving voltage of 40V has been demonstrated.

The first experimental results, to our knowledge, for the wavelength dependence of the electro-optic (EO) coefficients of a poled polymer film containing photochromic dyes are presented. The method used for measurement is based on the attenuated-total-reflection (ATR) technique. Initial results show that the electro-optic coefficients near absorption band decreases with the increases of light wavelength.

A novel cross-linked second-order nonlinear optical polyurethane was synthesized from disperse red 19 (DR-19), triethanolamine and the trimer (TTDI) of toluene diisocyanate. The thermal stability of the polyurethane was significantly improved because the trimer had high thermal stability and increased the cross-link degree and the rigidity of the polyurethane. The polyurethane obtained high poling efficiency through a novel "host-guest" approach, and the electro-optical coefficient γ₃₃ reached 37 pm/V at 832 nm. The propagation loss of the polyurethane was lowered because the number density of C-H bonds in the polyurethane was low and the films had good optical quality.

Si0₂ films were fabricated on Si substrates by flame hydrolysis deposition (FHD) as buffer layer of waveguides. The optical and surface properties of the films were characterized using scanning electron microanalyzer (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and variable angle spectroscopic ellipsometry (VASE). From a series of analyses, we demonstrated the excellent silica films fabricated. It proves that Si0₂ films prepared by flame hydrolysis deposition are entirely able to be applied in planar optical waveguides.

A new method based on aperiodically poled lithium niobate is suggested to provide multiple wavelengths for WDM optical communications applications. In this paper, we theoretically investigate the method for generating multi-wavelength source based on optical parametric oscillation (OPO) in aperiodically poled lithium niobate (APLN). We also check the effect of errors caused by the room-temperature electric poling process. The relationship between the line-width and the block length is also discussed.

Vanadyl-phthlocyanine (VOPc) thin films were prepared by a molecular beam epitaxy on a polyimide (PI) substrate at 150°C, and then they were exposed to dichloroethane vapor for 25 hours. Their morphologies were investigated with Vis/UV spectra and the surface images observed by an atomic force microscope (AFM). The Vis/UV spectrum of VOPc thin film before the organic gas treatment has a broad absorption shoulder between 640 and 740nm and an absorption peak at 840nm in the Q band region. It has been known so far that VOPc thin film has Phase I ,II and III. Phase I has two absorption peaks at 680 and 740nm. Phase II and Phase III are characterized with absorption peaks at 820 and 830nm, respectively. Therefore, the morphology having an absorption peak at 840nm is different from that of Phase 111 . The Vis/UV spectrum of VOPc thin film after the organic gas treatment has a broad absorption shoulder between 640 and 740nm and an absorption peak at 830nm in the Q band region. The absorption peak at 840nm shifts to 830nm by the organic gas treatment. This means that the phase morphology of VOPc thin film changes into Phase III during the gas treatment. On the other hand, VOPc molecules deposited on P1 substrate before the organic gas treatment form needle crystals. This indicates that VOPc molecules deposited on P1 substrate are perpendicular to PI substrate. The surface image of VOPc thin film after the gas treatment is smooth. This suggests that VOPc molecules are parallel to PI substrate. The third-order optical susceptibilities after and before the gas treatment are 3.75x10^-9 and 3.25x10^-9 esu, respectively. The molecular orientation of VOPc thin film is improved during the organic gas treatment.

Based on the arrayed waveguide grating (AWG) multiplexer theory, some important parameters are optimized for the structural design of a polymer AWG multiplexer around the central wavelength of 1.55μm with the wavelength spacing of 1.6 nm. These parameters include diffraction order, focal length of slab waveguides, number of arrayed waveguides are determined. Then, a schematic waveguide layout of this device is presented, which contains 9 input and 9 output channels. The transmission and loss characteristics are analyzed. The computed results show that when we select the core thickness as 4 micron, width as 6 micron, pitch of adjacent waveguides as 26 micron, diffraction order number as 78, distance between the focal point and the origin as 8340 micron, the total loss of the device can be dropped to about 5.7dB, and the crosstalk among output channels can be dropped below -50dB.

Excimer laser-induced crystallization (ELC) technique has been used to prepare nanocrystal silicon (nc-Si) from amorphous silicon (a-Si) thin films on silicon or glass substrate. The a-Si films without hydrogen grown by pulsed laser deposition (PLD) are chosen as precursor to avoid the problem of hydrogen effluence during annealing. The analysis has been performed by scanning electron microscopy (SEM), Raman scattering spectroscopy and high-resolution transmission electron microscopy (HRTEM). Experimental results show that the silicon nanocrystals can be formed by laser annealing. The growth characters of nc-Si are strongly dependent on the laser energy density. It is shown that the volume of melted Si essentially predominates the grain size of nc-Si, and the surface tension of crystallized silicon is responsible for the mechanism of nc-Si growth

The Nd:YVO4 single crystal was successfully grown by the Edge-defined film-fed growth (EFG) method. The crystal grown process was described in detail. The absorption and photoluminescence according to concentration of Nd ions in the Nd:YVO4 crystal have been measured. The wavelength of stronger absorption peak appeared around 596 nm, and that of the photoluminescence was the stronger at 879 nm.

Er and Mg co-doped LiNbO₃ single crystal with a melt concentration of 1, 3 mol% MgO and 0.6 mol% Er₂O₃ have been grown by the micro-pulling down method to study the Er and Mg incorporation into the LiNbO₃ matrix. Compositional uniformity of the grown crystals was estimated. The influence of Er ions on the optical properties of Mg:LiNbO₃ single crystals was investigated.

Polarization Mode dispersion (PMD) in single-mode fibers is a common source of problems in quantum key distribution (QKD) as well as all optical communication. Donald S. Bethune and William P. Risk developed a PMD-free phase modulator which is a single port component. We found that it is also necessary to construct a dual-port component. In this report, we demonstrate how PMD affects our single-photon interference experiment, and give a proposal on developing a dual-port PMD-free integrated phase modulator. This new component can be used in QKD as well as in other optical fiber communication schemes. And it will make long-distance information exchange more stable and effective.

Electron emission properties of doped In₂0₃ and Sn0₂ (ITO) thin layers have been studied. These layers have been deposited onto both surfaces of a microscope glass using a constant-current ion sputtering method. One of the layer (1 μm thick) was a field electrode and another one (1Onm - 200nm) was treated as an electron emitter. The layers were examined using an electron emission induced by electric field. The polarizing voltage U_pol has been applied to the field electrode. The studies has been carried out in vacuum (1O^-7 hPa). Electron emission yield dependence on the intensity of an internal field and illumination were measured. The exponential dependence of the pulse frequency n =f(U_pol) has been found. With increasing U_pol (field strength in a sample) and after illumination the count frequency of pulses grows monotonically. At low U_pol (≤|-500V|) the increase is linear. At higher U_pol this dependence is exponential. Energy analysis of emitted electrons was performed by the retarding field method. Measurements of electrons energy in field induced emission showed that about 80% of electrons have energy up to 10 eV. It was also found that additional effect at simultaneous emission oftwo electrons as result ofabsorption of a single photon have to be taken into account.

A novel dynamic transmission-line-laser-modeling-based model of the multiple phase shift distributed feedback (DFB) lasers has been proposed in this paper. The dynamic and static characteristics of three phase shift (3PS) DFB structures are analyzed based on this model. The longitudinal carrier density distribution of quarterly wavelength shifted (QWS) DFB LDs and 3PS DFB LDs are compared. Our results show that 3PS DFB structure has a more uniform longitudinal carrier density distribution; hence such a structure reduces the spatial hole burning effect and strengthens the stability of single longitudinal mode.

The oxidised porous silicon channel waveguides were fabricated by controlling the illumination intensities and anodisation time during anodisation process is reported in this paper. By the technique combined the optimisation end-fire coupling and cut-back methods, the relatively exact results of measured propagation loss, endface' s scattering loss and the mode mismatching loss of oxidised porous silicon channel waveguides were 12.5.2dB/cm, 4.6dB and 3.1dB respectively.

In this paper, we compared the effects of crosstalk in WDM systems using laser sources between using spectruinsliced light sources by using the Gaussian noise approximation. Compared with the system using laser sources, the intraband crosstalk in the system using spectrum-sliced light sources are uiuch Iess sensitive by signal power and crosstalk power, this is mainly because the spectrum-sliced light source have relatively broad optical bandwidth, the signal-crosstalk beat noise is reduced rapidly as the beat components become spread outside of the receiver's bandwidth.

Polarization controller (PC) for optical fiber is a major area of study in the general field of coherent-optical communication systems. In communication systems based on single-mode fiber, the states of polarization in fiber vary randomly due to temperature variations and mechanical perturbations along the fiber. These polarization changes can have a detrimental impact on polarization sensitive components. Recently, more and more research attentions have been paid to a new artificial nonlinear material: the periodically poled LiNbO₃ (PPLN) because of its outstanding nonlinear optical properties. In this paper, we analytically proposed an electrical tuned polarization controller based on a single chip of Z-cut LiNbO₃ crystal. The first part is a Z-cut lithium niobate and the second part is periodically poled. The electric field is applied along the transverse and longitude directions for the separated part to implement the electro-optical polarization controller, respectively. With two electric fields applied by special control algorithms, the first part can transform an incident light with arbitrary ellipsoid polarization into a linearly polarized light and the second part will turn this linearly polarized light to a fixed linearly polarized light. Furthermore, if we use PPLN waveguide to fabricate such a device, only about 10V maximum driven voltage is needed for each stage, which is very attractive.

A new optoelectronic integrated device consisting of an n-GaAs optical field-effect transistor (OPFET) and a p-AlGaAs/p-GaAs/n⁺-AlGaAs surface emitting double heterostructure light emitting diode (DH-LED) which are developed monolithically on a p⁺-GaAs subtrate and separated by a thin semi-insulating GaAs layer, is proposed in this paper. We call this device as Light Source Integrated-OPFET (LSI-OPFET). The proposed device structure is such that the optical radiation generated by the LED is fed into the OPFET as back illumination. The back radiation is used as the control signal to the OPFET which changes the transconductance of the OPFET. The intensity level of the back illumination to the OPFET can be controlled by changing the bias current of the LED. In this paper, analytical results have been presented for the I-V characteristics and transconductance of the OPFET as a function of the LED current. It has been shown that by changing the level of the back illumination to the OPFET, i.e. by changing the LED current, one can vary both the characteristics and transconductance, which makes the LSI-OPFET as the potential device for the optically controlled varying gain amplifier.

In this paper, we demonstrate two configurations (A and B) distributed Raman fiber amplifier (RFA) with near flatten bandwidth of 40 nm in the 1530-1570 nm region. The wavelengths of Raman pumps are 1445 nm and 1470 nm. The dual-pumped Raman amplifier includes two optical isolators, and two 1550/14xx nm WDM couplers. Inside RFA there are dispersion compensation fiber (DCF) fiber integrated single-mode fiber (SMF). The chromatic dispersion of DCF and SMF are -85 and +17 ps/nm-km, respectively, while the attenuation of them are 0.43 and 0.19 dB/km, respectively. For the measurement of polarization dependent gain, the maximum gain of 24 dB is achieved with gain variation of 3.5 dB for configuration A. For gain equalization issue, the gain variation among the 1530-1570 nm is decreased from 8.3 dB to 2.4 dB when appropriately adjust the individual pump power for configuration B. One 10 Gb/s modulated signal is used to confirm the bit error rate performance of RFA. Small power penalty of 0.7 dB is observed.

This paper describes the fabrication, operation, commercialization, and application of VCSELs operating at wavelength ranges from 650nm to 1600nm.

Three types of thin layer were inserted between 1st and 2nd separate confinement heterostructure (SCH) layer of 1.55 μm InGaAaP/InGaAs multi-quantum well (MQW) laser diodes. The three types were Type A (p-InGaAsP, 1x10¹⁷/cm³), Type B (p-InGaAsP, 2x10¹⁸/cm³), and Type C (p-InP, 2x10¹⁸/cm³), respectively. It was shown that the light-current (L-I) characteristics for those three types were similar, while the characteristic temperature (T₀) was higher for type B than others.

2.5Gb/s optical transmitter IC for vertical-cavity surface-emitting lasers (VCSELs) was fabricated using the TSMC 2-poly 4-metal process of 0.35μm Si-CMOS. This IC has four channels with 250μm pitch for VCSEL array. The transmitter IC consists of four parts, i.e., buffer, differential amplifier, threshold current controller and modulation current controller. Modifying the threshold current and modulation current, we attained a wide range of the operation current from 1mA to 20mA. The measurement of the IC chip packaged with a 850nm VCSEL array, we obtained a maximum optical output power of 2dBm in 2.5Gb/s operation and an extinction ratio of 5~25dB.

The theoretical analysis and experimental measurement on the angle dependence of quantum efficiency of GaAs based resonant cavity enhanced (RCE) photodetector is presented. By changing the angle of incoming light, about 40nm wavelength variation of peak quantum efficiency has been experimentally obtained. The peak quantum efficiency and optical bandwidth at different mode corresponding to different angle incidence have been characterized with different absorption dependence on wavelength. The convenient angle tuning of resonant mode will be helpful to relax the strict constraint of RCE photodetector to light source with narrow emission spectrum while especially applied in space optical detections and communications.

1.55 μm­ multi-quantum well (MQW) broad area laser diodes with different linewidth enhancement factor (a-factor) of 2 and 4 were fabricated. The far-fields of the laser diodes were measured. It was observed that the full width half maximum (FWHM) of the far-fields and the filamentations were reduced in the laser diodes whose α-factor is 2 rather than 4. As injection current increased, the FWHM of the far-fields also increased regardless of α-factor. This phenomenon was explained by reduction of filament spacing as injection current increased

We present here a theoretical study on the modifications of the Bragg grating response induced by the absorption of the U.V. light, when the grating is written in a 2x2 symmetric fused fiber coupler. In this particular case of a complex structure the direction of irradiation is very important as shown by wavelength response curves.

The Dy³⁺ doped silica glasses were prepared by sol-gel process with appropriate heat treatment. The structural changes during the gel to glass transition of the silica xerogels and the effect on fluorescence properties of Dy³⁺ were studied. For Dy³⁺ two dominant emissions occur at about 575nm(⁴F_9/2→⁶H_15/2) in the yellow region and 480nm (⁴F_9/2→⁶H_13/2) in the blue region. Both transitions are electric dipole in nature out of which (⁴F_9/2→⁶H_13/2) is hypersensitive. The intensity ratio (yellow to blue (Y/B)) of Dy³⁺ emission follows a trend parallel to the red to orange (R/O) ratio of Eu³⁺ in silica matrices. These ratios are influenced by the site symmetry and electro negativity of ligand atoms. The fluorescence intensity of Dy³⁺ ions increases remarkably when the doped xerogel is heat-treated. The fluorescence intensity ratio (Y/B) is used as a measure of the symmetry of Dy³⁺ environment during the gel - glass conversion, the higher the ratio, the more asymmetric is the environment. The high value of the intensity ratio of the 1000°C heated gel showed that the Dy³⁺ was embedded in the glassy silica network with an asymmetric environment. The FTIR and thermo gravimetric analysis (TGA) clearly showed the complete densification (density=2.2 gm/cm³) of the gels around 1000°C.

It is well known that when the laser is turned on by increasing the device current from its initial value Jo to the above-threshold value J greater than Jth, stimulated recombination is delayed by td, the time during which the carrier population rises to its threshold value. On the besis ofthe rate equations for quantum well VCSEL, a closed expression describing the time evolution of the carrier density within the turn-on period of a VCSEL has been derived for the case that the Auger effect is considered with a term proportional to the cube ofthe carrier density. The theoretic results are simulated with Simulink of MATLAB software. As a result, an explicit analytical expression for the turn-on delay of the VCSEL has also been deduced. Since the turn-on delay is an important parameter of a semiconductor laser, intensified studies on this parameter have been carried out in the past years.

The search, which deals with the reliability examination facility ofglimmer collimation mirror, fills up the blank of domestic corresponding province. It is credible and high effective to successfully authenticate the MTBF index of glimmer collimation mirror, at the same time advance the quality of examination, which has great meaning. In this paper, introduce both the whole system constitution of this facility and the synopsis of realization scheme about partly and main subsystems, which include optical stress subsystem, electric stress subsystem as well as inspection and register subsystem.

The effects of birefringence on performances of SOA-based interferometer devices are analyzed theoretically, the necessity of fabricating SOA whose gain and induced phase shift are both independent on polarization state is proposed. Birefringence in SOA will degrade the performances of SOA-based devices due to polarization walkoff of the two split probe light. The calculations for a SOA-based Mach-Zehnder interferometer wavelength-converter indicate that the extinction ratio will decrease and become very sensitive to the polarization state of input light if there is birefringence in SOAs. A scheme is proposed to eliminate these effects and the possibility of making a SOA polarization insensitive in gain and induce phase shift is analyzed theoretically.

Two configurations of distributed Raman amplifiers with dispersion compensation module are analyzed. On the basis of dispersion compensation, a lossless hybrid line is obtained. And amplifier characteristics such as gain and noise figure are compared between the two configurations. The results show that the SMF+DCF configuration is a good candidate at low pump conditions.

The impact of multipath interference (MPI) on the noise figure of fiber Raman amplifier is studied. The noise figure is analytically expressed in terms ofthe Raman gain and the Rayleigh scattering parameters ofthe Raman fiber. The difference between the power spectral characteristics of the multipath interference noise and that of the Raman spontaneous emission noise is considered in this paper. We demonstrate that the MPI can be a significant degrading factor to the noise figure when the Raman on-off gain and the input signal power are increased. A modified noise figure measuring method is proposed so that the noise figure accounts for the MPI deriving from the sum of Rayleigh backscattering signal components.

This paper aims at numerically simulating gain recovery enhancement effect in SOAs when a CW pump light is applied. An effective carrier lifetime model was given and used to investigate the pump power and wavelength dependence of SOA effective carrier lifetime. Effective carrier lifetime reduction behaviors and gain saturation curves at the signal wavelength were simulated. Gain dynamics introduced by short pulse amplification in a CW pumped SOA were also simulated to visualize the recovery enhancement effect.

The cascadability of Semiconductor optical amplifier (SOA) gates and the size limitations for several kinds of switch architectures based on SOA's are studied theoretically. The analysis shows that the sizes of matrix-vector switches are severely limited owing to the splitting losses, waveguide losses and coupling losses. However for distributed gain matrix-vector switch and Benes switch, the accumulation of amplified spontaneous emission (ASE) noise and non-ideal extinction ratio also greatly influence the maximal sizes of switches. The calculation results also reveal that the gain optimum strategy for switches based on SOA's, which derived from steady state analysis, will not be optimum when non-ideal extinction ratio and dynamical gain saturation is considered

A new scheme for studying dynamics process of semiconductor optical amplifier (SOA) in quantum wells structure (QWS) is proposed based on A-type three-level model. When the system is off-resonantly excited by incoherent light beams, the interaction process can be regarded as a coherent Anti-Stokes Raman scattering (CARS). The signal behavior determined by ultrafast process of sub-valance-band (SVB) are analyzed by the transient incoherent spectroscopy based on CARS. If the broad-band light resource as light emitting diode(LED) is utilized in experiment, the time resolution extends femtosecond-resolved. This experiment scheme which is composed of LED ,multimode fiber and the other devices is rather useful to investigate the carrier relaxation time between the two SVl3s.

Based on analytical continuation of the round-trip condition, in contrast to existing rate equations. Threshold current density, slope efficiency, and threshold gain of cascade VCSEL as a function of number of active regions for the different size-dependent paramenters such as the cavity of length and thickness of each active region are discussed as applications. The results showed behavior of an almost linear increase in slope efficiency and a reduction in threshold current density with the number of stages.

Er³⁺-doped A1₂0₃ thin films are deposited on silicon substrates by reactive closed-field unbalanced magnetron sputtering(CFUBMS).The process parameters,such as target bias voltage, substrate bias voltage, 0₂ gas flows, sputtering gas pressure,are studied.The thin film properties of interest are Al/O ratio,thickness,refractive index,crystallographic structure and surface roughness. 1.53μm photoluminescence(PL) characterization pumping at wavelength 980nm is measured.The relationship between PL peak intensity and different anneal temperature, and different pumping power is experimental investigated.

The phenomena of homodyne and resonating in optical fiber rings (OFRs) are experimentally investigated. The beat noise characteristics in passive OFRs and active OFRs are revealed. The beat noise spectra of OFRs and homodyne interferometer with the same length of delay fiber line are compared. A substitute homodyne interferometer configured by band-reject OFR is proposed.

The capacity of channel is tha highest data rate it can reliably support.Whenever the data rate is less than the capacity of the channel, there exists an error-correcting code for the channel that has an output probability of error as small as desired, and coversely, whenever the data rate is more than the capacity the probability oferror is bounded away from zero. The capacity is determined an optical channel employing Pulse Position modulation (PPM) and an Avalanche Photodiode (APD) detector. The channel is different from the usual optical channel in that the detector output is characterized by a webb-plus-gaussian distribution, not a poisson distribution. The capacity is expressed as a funtion of the PPM order, solt width ,laser dead time , average number of incident singal and background photons received, and APD parameters. Based on a system using a laser and detector proposed for x2000 second delivery, numerical results provide upper bounds on the data rate and level of background noise that the channel can support while operating at a given BER For the particular case studied, the capacity-maximizing PPM order is near 2048 for nighttime reception and 16 for daytime reception. Reed-Solomon codes can hanndle backgroun levels 2.3 to 7.6 dB below the ultimate level that can be handled by codes operating at the Shannon limit.

The backscattering spectrum of optical fiber G652 (SiO₂) has been researched, in the Stokes region the first order and second order Raman spectrum have been observed and the ZX band backscattering spectrum is first observed. The small signal pump on/off Raman gain spectrums have been measured by the 1427.2nm Raman laser and Q8384 optical spectrum analyzer, during different pump power. The Raman gain is 19dB and gain band width is 96nm (1440nm-1536nm) during the pump power is 700mw. The liquid-core optical fiber is made ofhollow quartz fiber filling organic liquid materials including C₆H₆, CS₂, CCl₄ and so on. The constitution and proportion of liquid materials are designed. Raman effect in liquid-core optical fiber is researched. The liquid-core optical fiber Raman amplifier are designed by using FRA optimum design software. This observed Stokes frequency shift is characteristic of the 992-cm^-1, 656-cm^-1, and 459cm^-1 lines in C₆H₆ CS₂, andCCl₄. The Raman laser (1427mm) is used as pumping laser. A mini-ASE light source is used as signal source. The Raman spectrum has been measured by OSA Q8384 in liquid-core optical fiber. The Raman amplified bandwidth in liquid-core optical fiber is researched. The relations between the pumping threshold and liquid-core optical fiber length are attained.

The light localization due to defects and disorder and its effects on light propagation in one-dimensional (1D) photonic band gap (PBG) structures is studied numerically with transfer matrix method. For a defect layer embedded at the center of a I D PBG structure, the simulation results indicated that, the photons will be trapped in the defect region. For a disordered I D PBG structure, a mechanism for extension of the transmission band gap is illustrated with combining the effects of Bragg reflection and Anderson localization. We propose that, analog to disordered semiconductors, there may exist two band gaps in disordered PBG structure: transmission gap and mode-density gap.

A computing model to calculate the small-signal gain and noise figure ofa multi-wavelength-pumped fiber Raman amplifier (FRA) was developed. The properties and several elemental principles for the design of multi-wavelength-pumped FRA were discussed and its noise figure was analyzed at the same time. Finally, a 12-wavelength-pumped FRA using WDM diode pumps with an outstanding performance such as 2.5dB flatness over 9Onm was designed by using the model.

Optimum design of S-band negative dispersion DCF discrete fiber Raman amplifier has been researched by OPTIAMP DESIGN 3.3 SOFTWARE (made in Canada Optiwave Corporation). Simulated result is following: The optimum fiber is 6.4km. The small signal pump on/off gain spectrums have been got, During different back-direction pump power. The backscattering spectrum of optical fiber has been measured by use 1427nm Raman laser and Q8384 optical spectrum analyzer and Stokes and anti-Stokes ZX band backscattering spectrum has been first observed and discussed, zx band frequency shift is 1THz, band width 3THz(3dB).gain spectrum and gain vs. power of DCF discrete fiber Raman amplifier have been measured, practical including Stokes ZX band backscattering gain effect. Pump on/off small signal gain is 13dB (pump power 700mw; fiber 5. 1km) and gain band width is 88nm (1440nm-1528nm).

The bi-directional optical devices used in the analog and digital transmission system are introduced in this paper. Especially applied in the broadband access network (Cable Modem & xDSL). We developed a serious of products according to the different demands like PTP, HFC and PON. Applied in the CDMA optical repeater is also discussed, 1310/1550nm and CWDM bi-directional optical device can be used in the traditional and low cost approach.